New Liquid Crystals Comprising Photoisomerizable Cores for High Efficiency Solar Energy Harvesting and Storage

The aim of this proposal is to produce new energy conversion and storage materials that can be used as solar-thermal fuels (absorbing sunlight and releasing it as energy on demand). With Oman among the countries receiving the most sunlight worldwide, the proposed research here is of strategic importance. The current market of renewable energy is dominated by photovoltaic devices that harvest some of the energy in sunlight. However, this energy is transformed into electricity, which is difficult to store in a cost-effective manner. Solar-thermal fuel is an alternative approach in which the solar energy is converted to heat that can easily be stored for a long time, thus generating power on demand. In this project we will synthesize, characterize and test new liquid crystalline materials capable of storing the harvested sunlight by chemical transformation and releasing this energy with high efficiency. The new materials will include chemical core structures that are capable of undergoing photoisomerization upon exposure to light. The photoisomerization process will produce polar domains. We will confine these domains in liquid crystal relaxors that are capable of reversibly storing and delivering the absorbed light energy. We will synthesize new derivatives of azobenzene as the core compounds because of the high potential of azobenzene for energy harvesting due to its clean, i.e. without byproducts, and efficient reversible trans ? cis photoisomerization, and its ability to form aggregates. The liquid crystals chosen are organic materials that we successfully utilized in our recent work on energy storage. These liquid crystals efficiently respond to external stimuli, such as light or electrical fields, which can be used to control charge transport in electrolytes. Liquid crystals are also attractive candidates as organic energy harvesters due to their combination of short range molecular mobility (which promotes conductivity), long-range order (which promotes ferroelectricity), and their self-healing character (which yields long-range effective charge transfer). The new materials (core compounds embedded in liquid crystals) will be characterized optically, electrically, chemically, and structurally in order to optimize their efficiency. The initial results will be used as a benchmark for structural modifications in the core compounds that are aimed at improving their spectroscopic properties, such as broadening and shifting their light absorption to the visible region of the solar spectrum for more efficient solar energy harvesting. The new materials will be evaluated by measuring their energy density and power density. The proposed work here will contribute to unleashing the almost unlimited potential of solar light irradiation on earth to cover energy demands using renewable sources.